1. Field of the Invention
The present invention relates to an integrated PET/CT system providing an integrated PET/CT picture by simultaneously sequentially taking a PET picture and a CT picture with one system, and more particularly, to an integrated PET/CT system providing a simple and excellent integrated PET/CT picture by using an integrated PET/CT detecting module formed by integrating a flat-panel x-ray detector with a PET detector.
2. Description of Related Art
Integrated PET/CT composite image apparatuses are medical equipment used for oncology, neurology, cardiovascular medicine and other diagnosis picture and considerably increases diagnosis accuracy by effectively integrating the functional picture provided by the PET and the anatomical picture provided by the CT; therefore, the excellence and necessity has already been clinically proved and demand has rapidly increased in the past several years.
The initial PET and CT composite picture was acquired by simply combining pictures taken by PET and CT systems, but it was difficult to combine the pictures and there were errors in the composite picture because the conditions are different in taking the pictures and movement of patients and organs. Further, patients have to move to two systems at different position to take the pictures, such that there were various problems.
In order to solve the problem, several studies and patents have been proposed around 2000 and representative studies are D W Townsend, “A combined PET/CT scanner: the choices”, Journal of Nuclear Medicine, 2001: 3:533-534, and R, Nutt, D W Townsend, “Combined PET and X-ray CT tomograph”, U.S. Pat. No. 6,631,284, 2003, which have proposed an integrated PET/CT system by combining PET and CT equipment.
Recently, a demand for the combination product of PET/CT system has been gradually increasing, and the integrated PET/CT products manufactured by combining PET and CT is 95% or more in the entire PET market.
However, the studies and patents of D W Townsend or R. Nutt have proposed simple combination of individual PET system and CT system, which is a little different from an integrated PET/CT system in the true sense of the word.
As shown in FIG. 1, an integrated PET/CT system 91 according to the related art is a product formed by simply combining two apparatuses of a PET apparatus 81 and a CT apparatus 80, which is a little different from the integrated PEC/CT system in the true sense of the word.
Further, since two large apparatuses are combined, the volume of the equipment increases and occupies a large space. Further, the length of the tunnel through which a patient passes to take pictures becomes long, such that the patient's anxiety increases. Further, since a patient has to pass through a long tunnel in the systems of the related art, a relatively long patient pallet 72 was required and accordingly the patient pallet bends when moving to the rear portion of the system, thereby make errors in the pictures.
In order to overcome the problems, the present invention, as shown in FIG. 2, proposes an integrated PET/CT system in the true sense of the word which has a PET and a CT combined in one gantry by using an integrated PET/CT detecting module. The integrated PET/CT equipment takes pictures of the same object in terms of space and time, such that it provides better composite pictures and other advantages by implementing a simple system.
A prior study having a similar concept to the integrated PET/CT proposed in this study has been proposed in U.S. Pat. No. 6,449,331, 2002, titled “Combined PET and CT detector and method for using same”, by R. Nutt. However, the basis configuration of the detector and the method of processing pictures are remarkably different from the present invention. The principle of the method proposed in the above patent is to share a common PET detector to take PET and CT pictures and the PET and CT signals are collected and processed through different process circuits. Similarly, there were “A novel APD-Based Detector Module for Multi-Modality PET/SPECT/CT Scanners”, by A. Saoudi et. al, IEEE transaction in Nuclear Science, 46:3:479-484, 1999, and “Simultaneous Emission and Transmission Measurements for Attenuation Correction in Whole-Body PET”, by SR Meikle, et. al, The Journal of Nuclear Medicine, 36:9:1680-1995. However, in these prior studies, in the same as the proposal of R. Nutt, x-ray pictures are acquired from a common PET detector or a CT picture is acquired by using a gamma ray using a transmission radiation source.
The most important problem of the prior studies and patents is not providing high-resolution CT pictures satisfying the required conditions of recent composite pictures, because the resolutions of the CT picture and the PET detector are the same, and it is difficult to technically implement the composite picture.
A feature of the present invention that is remarkably different from the prior studies and patents is to mount a flat-panel x-ray detector at the front end of a PET detector to acquire CT pictures. As shown in FIG. 3, using the thin flat-panel x-ray detector provides high-resolution CT pictures while minimizing attenuation and scatter of the gamma ray in taking a PET picture.
In general, the flat-panel x-ray detector is mainly used in applications, such as the x-ray angiography or an x-ray digital moving imaging, and recently, a technology implementing an x-ray CT by using the above has been given a patent in the United States, in 2002, by Y. Ionue, et. al. (“X-ray CT apparatus” U.S. Pat. No. 6,373,916). A feature of the CT using the flat-panel x-ray detector is to take a picture of a wide field of view (FOV) without moving a patient by using a wide flat-panel x-ray detector and extending the existing fan beam to an x-ray cone beam.
Describing a difference of the present invention and the patent of Y. Ionue, first, the flat-panel x-ray detector rotates with an x-ray source or tube in the proposal of Y. Ionue. However, in the present invention, as shown in FIG. 5, a PET/CT detector module is mounted and fixed to a stationary gantry and one or a plurality of x-ray tubes rotates along the side of the gantry, which is the fourth generation CT system structure. Further, the size and shape of the flat-panel x-ray detector take the size and shape of the PET, which is also different from the patent of Y. Ionue.